1. Field
The embodiments discussed herein are directed to a storage controller and a firmware updating method and, more particularly, to a storage controller and a firmware updating method allowing cache data mirroring to be accomplished even during firmware update.
2. Description of the Related Art
In some of storage units such as disk array units, redundancy is provided in the internal construction to improve the reliability. For example, conventionally in a disk array unit redundancy may be provided in components including a channel adapter which is an interface for connection to a host computer and a central processing section for controlling input/output processing. The disk array unit may also have the function of duplicately holding cache data stored in a memory of one of two central processing sections by mirroring the cache data to a memory of the other central processing section for the purpose of improving the reliability of data.
Although a storage unit, which performs cache data mirroring for improving the reliability of data, can continue to operate at the time of firmware update, it has a problem of considerable reduction in performance. This is because operation in a write-back mode in which write to a disk is performed asynchronously with the operation of a host computer cannot be performed during firmware update, and operation in a write-through mode inferior in performance than the write-back mode must be performed during firmware update.
During firmware update, redundant structures such as central processing sections have different versions of firmware. Therefore, one line of the redundant structures which has been updated and another line which has not been updated may have different locations on memories allocated to the areas where cache data is stored. If cache data mirroring is performed when such an inconsistency exists between the areas, a serious fault such as area destruction may occur. In conventional storage systems, therefore, cache data mirroring is stopped during firmware update.
In a state where cache data mirroring is not being performed, cache data which has not been written to a disk is not sufficiently protected. If a serious fault occurs in the line whose cache data is held in a memory, the data may be lost. During firmware update, therefore, conventional storage systems can only be operated in the write-through mode in which write to a disk is immediately performed at a write request.